Patent GB-1247374-A (GB)
Title: A ceramic treatment process
IPC: C04B41/85
Filed: 1968-11-11
Abstract: 1,247,374. Refractory bodies and coatings. KAMAN SCIENCES CORP. 11 Nov., 1968 [28 Dec., 1967], No. 53403/68. Addition to 1,234,043. Heading CIJ. [Also in Divisions B2 and C4-C5] Refractory bodies are made by forming an unsintered porous structure from a mass of particles at least the surface of which comprises at least one metallic oxide, impregnating the structure with a metallic compound, heating the structure to convert the metallic compound to a metallic oxide and to harden the structure, and then repeating the impregnation and curing steps at least once more. Suitable oxidic materials from which the porous structure can be formed are those of aluminium, barium, beryllium, calcium, cerium, chromium, cobalt, copper, gallium, hafnium, iron, lanthanum, magnesium, manganese, molybdenum, nickel, niobium, tantalum, thorium, tin, titanium, tungsten, uranium, vanadium, ytrrium, zinc, zirconium and mixtures of these. The porous structures can contain reinforcing metal or ceramic fibres and kaolin as a binder. Suitable impregnants are aqueous solutions of chromium trioxide, cerrous nitrate, zirconyl chloride, cobalt nitrate, nickel nitrate, titanium oxalate, silicotungstic acid, magnesium chromate, beryllium nitrate, chromium sulphate and chromium chloride. After repeated steps of impregnation with the metallic compound and heat curing the structure can be impregnated with phosphoric acid and then heated to further harden it. The unsintered porous structures can be formed by extruding a slurry of the particles which also contains kaolin as a plasticizer and temporary bond and optionally chromic acid, by slip casting a slurry of the particles which also contains kaolin, chromic acid or chromium chloride, by pressing the powder with some chromic acid, polyethylene glycol or water, or by packing the particles into a closed mould and impregnating with chromic acid and heating to cure before removing the structure from the mould. Hard coatings are formed on the surface of metal, glass or ceramic materials by providing the surface with a porous unsintered coating of metallic oxide, boron oxide, silicon dioxide, boron carbide or silicon carbide, impregnating the material of the coating before or after its application to the surface with chromic acid, heating the impregnated coating to cure and harden the coating and bond it to the said surface, and then repeating the impregnation and heat curing steps. A coating of powdered metal, which becomes coated with oxide on impregnation with chromic acid, can be used as the porous unsintered coating. Abrasive structures are produced by forming a porous unsintered body of particles of ground glass, glass or ceramic fibres, boron carbide, silicon carbide or other refractory abrasive material and hardening the structure by the repeated steps of impregnating with chromic acid and heating to a temperature between 600‹ and 1500‹ F. Fused, sintered, extruded or pelletized grain can be coated with a slurry of finely divided refractory oxide and/or kaolin before being hardened by repeated impregnation with chromic acid and heat curing. The hardened grain can be formed into resin bonded wheels.